Advances in satellite communication and related technology have led to rapid deployment of mobile satellite services (MSS) in recent years. While economic factors have slowed the growth of these systems, tens of thousands of user terminals are currently in use, providing valuable services in areas that otherwise would not have communications services.
Delivery of mobile satellite services, in addition to the user terminals, typically includes the provision of space vehicles, i.e. satellites, and a number of gateways, also referred to as base stations. The satellites serve as “relays” between the gateways and the user terminals.
Power controls are often employed to manage the exchange of signals between a user terminal and a gateway via one or more satellites. In particular, power control instructions, in the form of e.g. power control bits, are often included in or with the transmission frames received on a reverse link of a channel (also referred to as a return link of the channel).
In the context of MSS, a channel corresponds to an assigned frequency. In the context of multi-access, such as in the case of Time Division Multiple Access (TDMA), a channel is divided into multiple time slots, with one or more time slots assigned to each user terminal. The aggregate of these time slots, plus some overhead data bits, corresponds to a transmission frame. Analogously, in the case of Code Division Multiple Access, a channel is shared among simultaneous users by encoding the transmissions for each user with an orthogonal or nearly orthogonal spreading code.
Increasing the number of users, and the usage by the users, results in increased data traffic, which in turn translates into an increased amount of transmissions from the user terminals and processing to be performed by the gateways. To facilitate handling of the increased amount of processing, some gateways may desire to queue the transmission frames received on the reverse link of a channel and process them in batches.
Power control is important in CDMA systems for optimal capacity, so each transmission frame for user traffic (e.g., voice or data) typically carries a power control instruction (typically a single bit, indicating power up or down one increment) for the transmitter at the other end of the communication link. If the power control instructions are responded to in the same manner in the queued/batched processing context as they are responded to in the real time non-queued/un-batched processing context, acting upon excessive consecutive identical power control commands might result due to the delay inserted in the power control loop by the queuing. In turn, the excessive consecutive issuance of identical power control commands may lead to the loss of the channel or communication link.
Thus, an improved approach to responding to power control instructions, when transmission frames are queued or processed in batches, is desired.